1. Field of the Invention
The present invention relates to a network system and a communication device constituting the network system. More particularly, the present invention relates to a network system in which, in response to a request from a communication device, another communication device provides services; to a communication device for use therewith; to a processing method for use therewith; and to a program for enabling a computer to perform the processing method.
2. Description of the Related Art
As digital devices typified by a computer have become popular and those devices have been introduced into each household, how those devices can be easily handled has become a problem irrespective of the user. In particular, general users having no expertise knowledge are confused as to how the purchased devices are to be connected to construct a system. Furthermore, there is a risk in that, with the settings being insufficient, it is difficult to fully utilize the functions possessed by the devices.
In order to solve such problems, functions for allowing a newly introduced device to be used as is without performing a special setting have been proposed. For example, in the universal plug and play (UPnP: Universal Plug and Play), devices can be connected to a network without setting the network. More specifically, processing such that an IP (Internet Protocol) address is dynamically obtained, content of services that can be provided by the device itself is reported, content of services that can be provided by another device is obtained is performed so as to make preparations necessary for the subsequent control among the devices.
As described above, in order to perform device control in the network, it is necessary that the attributes of each device be mutually known in advance. For example, in the UPnP, since each process is performed using an IP layer, which is a network layer, it is presupposed that a host system for processing the IP layer is always in a running (wake) state. For this reason, the timing at which the host system is placed in a standby (sleep) status is limited, and it is difficult to reduce power consumption. Furthermore, in this UPnP, assuming that each device connected to the network is in a running status, communication based on broadcast or multicast is often used among the devices. Therefore, not only is the power consumption increased, but also the amount of communication data is increased.
In comparison, in a network system of the related art, a technology has been proposed in which, for the purpose of reducing power consumption, a server performing proxy pickup in place of a device in a standby status is provided, and the server returns the device from the sleep status to the running status when a message for the device in the wake state is received (refer to, for example, Japanese Unexamined Patent Application Publication No. 2000-165419 (FIG. 1)).